An emulsion of Omani heavy crude oil was prepared to reduce its viscosity, and combusted in a test boiler to investigate its combustibility and to analyze its flue gas composition, e.g., CO, SO2, NOx, and dust. The emulsion was evaluated to be suitable for use as a combustion fuel due to its lower environmental impact and lower possibility of high-temperature corrosion of boiler materials, in comparison with a commercial emulsion fuel, Orimulsion.